JP5581722B2 - Method for manufacturing foam insulated wire - Google Patents

Description

The present invention relates to a method for manufacturing a foam insulated wire obtained by kneading a different polymer material in a base resin.

  With the development of information communication networks in recent years, communication wires are required to have higher speed and larger capacity.

  In order to achieve high speed and large capacity, high-speed transmission wires often employ a differential transmission method in which positive and negative voltages are applied to a pair of two-core wires that are resistant to external noise.

  In such high-speed transmission wires, in order to improve characteristics such as a delay time difference at high frequencies, it is required to lower the dielectric constant of the insulator. Generally, a method of lowering the dielectric constant by foaming the insulator is generally required. It is used.

  Since the dielectric constant of the foamed insulator is lower as the foaming degree is higher, a higher foaming degree is required.

  In the differential transmission method, it is required to reduce a time difference (delay time difference: skew) required for two core wires to transmit a signal.

  The speed at which the two core wires transmit a signal depends on the dielectric constant of the foamed insulator covering the conductor, and therefore it is necessary that the dielectric constant is uniform, that is, the degree of foaming is uniform.

  An ideal foam is one in which bubbles having a uniform cell diameter are evenly distributed.

  If the degree of foaming is the same, the smaller the bubble diameter, the larger the number of foams, so the contribution to the degree of foaming of each individual bubble becomes smaller.

  That is, if the foam has a small bubble diameter and a large number of bubbles, slight fluctuations in the number of bubbles can be ignored.

  For this reason, it is considered that a foamed body having a uniform bubble size, that is, a dielectric constant having a uniform dielectric constant, can be obtained with a foam composed of bubbles having a uniform cell diameter.

  As a secondary effect, it can be expected that as the foam diameter is uniformly reduced, the stress at the time of bending is more easily dispersed, so that the stability of the mechanical strength is also improved.

  As described above, it is effective that the foamed insulator for electric wires used in the differential transmission system has a uniform bubble size by making the bubble diameters small.

  As described above, for high-speed transmission, the foamed insulator covering the conductor is required to have a low dielectric constant, and the differential transmission method is required to have a uniform dielectric constant.

  Furthermore, since electric wires are often used by bending, the foamed insulator is required to have mechanical strength.

  From the above, the foamed insulator used for the high-speed transmission wire adopting the differential transmission method is required to have a high foaming degree, a uniform foaming degree, and a small bubble diameter.

  As a foaming method for forming a foam insulator, generally, a method using a chemical foaming agent (chemical foaming), and a gas is injected into a molten resin in a molding machine (foaming extruder), inside and outside the molding machine. There is a method of foaming by a pressure difference (physical foaming).

  Chemical foaming has the advantage of easily obtaining a foam insulation with little variation in the degree of foaming, but it is difficult to achieve a high degree of foaming, and the residue of the foaming agent often has a high dielectric constant, so it is compared to the degree of foaming. As a result, the dielectric constant of the foamed insulator increases.

  For this reason, foamed insulators manufactured by a physical foaming method are frequently used for electric wires and cables for high-speed transmission.

JP 2005-271504 A

  In physical foaming, organic and inorganic particles called foaming nucleating agents are often mixed into the base resin. However, foaming nucleating agents often have a higher dielectric constant than the base resin, compared to the degree of foaming. The dielectric constant of the foam insulation is increased, the fine foam nucleating agent has a strong cohesive force and exists in the base resin in an aggregated state, so the number of foam nucleating agent particles is reduced compared to the amount added, etc. There is a problem.

  Therefore, the bubble diameter is large compared with the amount added, the foaming degree is low, and the problem that the foaming degree becomes uneven may occur.

Therefore, an object of the present invention is to solve the above-mentioned problems and provide a method for producing a foam insulated wire capable of producing a foam insulator having a small bubble diameter, a high foaming degree, a uniform foaming degree and a low dielectric constant. It is in.

  In order to achieve the above-mentioned problem, different polymer materials that have a lower dielectric constant than the above-mentioned foam nucleating agent and are uniformly dispersed in the base resin by kneading are kneaded into the base resin, and the difference in physical properties between the two is utilized. The present inventors have intensively studied to produce a foamed insulator that generates bubbles at the interface, has a small bubble diameter, a high foaming degree, a uniform foaming degree, and a low dielectric constant, and has achieved the present invention.

The invention of claim 1 is formed by kneading a polymer material different from the base resin into the base resin, and is dispersed in the base resin by processing at a predetermined processing temperature and injecting a foaming gas. foamed resin composition foaming extrusion to form a foam by foaming from the surrounding polymeric material of said heterologous to a process for the preparation of foam insulated wire coated with a foamed insulation on the outer periphery of the conductor, the base resin Is made of polyolefin resin, and the different polymer material is any one of polybutylene, cellulose, cellulose acetate, cellulose butylacetate, and polylactic acid, and the melting point of the different polymer material is the melting point of the base resin. a method for producing a foam insulated wire, characterized in that within the scope of the processing temperature.

The invention of claim 2 is formed by kneading a polymer material different from the base resin into the base resin, and is dispersed in the base resin by processing at a predetermined processing temperature and injecting a foaming gas. foamed resin composition foaming extrusion to form a foam by foaming from the surrounding polymeric material of said heterologous to a process for the preparation of foam insulated wire coated with a foamed insulation on the outer periphery of the conductor, the base resin Is made of polyolefin resin, the different polymer material is any one of polybutylene, cellulose, cellulose acetate, cellulose butylacetate, and polylactic acid, and the glass transition point of the different polymer material is the base resin a method for producing a foam insulated wire, characterized in that the melting point within the range of the processing temperature.

The invention according to claim 3 is the foam according to claim 1 or 2, wherein the dissimilar polymer material is 0.1 mass% or more and 45 mass% or less with respect to 100 mass% of the base resin and the dissimilar polymer material as a whole. It is a manufacturing method of an insulated wire .

Invention of Claim 4 is a manufacturing method of the foam insulated wire of Claims 1-3 whose foaming degree of the said foam insulation is 50% or more and 90% or less.

ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the foam insulated wire which can manufacture the foam insulation with a small bubble diameter, high foaming degree, uniform foaming degree, and a low dielectric constant can be provided.

It is a cross-sectional view of the foam insulated wire which concerns on one embodiment of this invention. It is a cross-sectional view of the coaxial cable which formed the foaming insulator using the foamed resin composition of this invention.

  Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

  First, the foamed resin composition of the present invention will be described.

  The foamed resin composition according to the present embodiment is obtained by kneading a different polymer material with a base resin.

  As the base resin, a polyolefin resin or a fluorine resin may be used.

  Polyolefin resins include polyethylene (PE), polypropylene (PP), ethylene-propylene copolymer, implant type TPO, ethylene-propylene-butene copolymer, ethylene-butene copolymer, ethylene-octene copolymer, ethylene A hexene copolymer or an ethylene-pentene copolymer may be used.

  Examples of PE include ultra high molecular PE, high density PE, medium density PE, low density PE, linear low density PE, and ultra low density PE. Examples of PP include block polypropylene, random polypropylene, atactic polypropylene, syndiotactic polypropylene, and isotactic polypropylene.

  Examples of fluororesins include polytetrafluoroethylene (PTFE), ethylene-tetrafluoroethylene copolymer (ETFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and tetrafluoroethylene-perfluoroalkoxyethylene copolymer. (PFA), polychlorotrifluoroethylene (PCTFE), ethylene-chlorotrifluoroethylene copolymer (ECTFE), polyvinylidene fluoride (PVDF), and polyvinyl fluoride (PVF). These may be used alone or in combination.

  In particular, a resin in which low density PE and high density PE are mixed is suitable.

  As the base resin, for example, a mixture of HDPE of about 10 to 90 mass% and LDPE of about 90 to 10 mass% may be used with respect to the total resin composition.

  In this Embodiment, what mixed HDPE0-99.9 mass% and LDPE99.9-0mass% was used with respect to all the resin compositions.

  Base resins include colorants, antioxidants, viscosity modifiers, reinforcing materials, fillers, plasticizers (softeners), vulcanizing agents, vulcanization accelerators, crosslinking agents, crosslinking aids that can be added for electrical insulation applications. Agent, foaming aid, processing aid, anti-aging agent, heat stabilizer, weather stabilizer, antistatic agent, lubricant, UV absorber, light stabilizer, flame retardant, surfactant, compatibilizer (compatibility) Agent) and other additives may be added as appropriate.

  Examples of the flame retardant include metal hydroxides, phosphorus flame retardants, silicone flame retardants, nitrogen flame retardants, boric acid compounds, molybdenum compounds, and metal hydroxides are preferable from the viewpoint of environmental considerations. is there. Examples of the metal hydroxide include magnesium hydroxide, aluminum hydroxide, and calcium hydroxide, and magnesium hydroxide having a high flame retarding effect is preferable.

  When the base resin is a polyolefin resin, examples of the different polymer material include polybutylene, cellulose, cellulose acetate, cellulose butylacetate, and polylactic acid. Any resin can be used as long as it is within the range from the melting point of the resin to the processing temperature of the foamed resin composition.

  Here, the processing temperature of the foamed resin composition refers to the temperature of the resin in the extruder measured by opening a hole in the neck portion of the foaming extruder and inserting a thermocouple.

  The dissimilar polymer material may be added in an amount of 0.1 mass% to 45 mass% with respect to 100 mass% of the total resin composition to be mixed.

  This is because when the amount (concentration) of the different polymer material is less than 0.1 mass%, the bubble diameter and the foaming degree are often the same as when the different polymer material is not added, and 45 mass% is reduced. This is because exceeding the range often has an adverse effect on electrical properties and mechanical strength.

  The addition amount of the different polymer material is preferably 0.5 mass% or more and 40 mass% or less, more preferably 1 mass% or more and 25 mass% or less, but is not limited to this. What is necessary is just to make it select suitably according to the thickness of the foaming insulator produced using a resin composition, a foaming degree, and various required characteristics.

  The manufacturing method of the foamed resin composition which concerns on this Embodiment is demonstrated.

  In the method for producing a foamed resin composition according to the present embodiment, different types of polymer materials are kneaded into the base resin.

  There are many methods for adding different types of polymer materials to the base resin, and examples include a dry blend method, a master batch (MB) method, and a full compound method.

  In the dry blend method, different types of polymer material and base resin are directly supplied to a molding machine (for example, a foaming extruder).

  In the MB method, for example, a MB is prepared by mixing different types of polymer materials into a part of the base resin or a part of the resin material constituting the base resin or a completely different resin from the base resin using a kneader or the like. The prepared MB and a base resin not containing a different polymer material are mixed in a molding machine (for example, a foaming extruder) to obtain a foamed resin composition.

  In the full compound method, a full compound in which a predetermined amount of different polymer materials are kneaded with a base resin is produced by an arbitrary method, and the produced full compound is supplied to a molding machine (for example, a foaming extruder).

  The above-described typical kneading methods for different kinds of polymer materials and base resins are not particularly defined for the method for kneading different kinds of polymer materials and base resins.

  The operation of the foamed resin composition according to the present embodiment will be described.

  By kneading the different polymer material and the base resin, an interface between the base resin and the different polymer material is generated.

  During processing of the foamed resin composition, the foaming gas is dissolved in the different polymer material and the base resin.

  When the foamed resin composition is extruded from the foaming extruder and cooled, the vitrification or crystallization of the different polymer material occurs earlier than the crystallization of the base resin.

  With the vitrification or crystallization of the different polymer material, the foaming gas dissolved in the different polymer material is expelled from the different polymer material.

  As a result, the foaming gas concentration of the base resin near the interface with the different polymer material is increased. Therefore, bubbles are likely to be generated in this region, and the interface is considered to be a starting point for generating bubbles.

  That is, there is a problem that the bubble diameter is large, the foaming degree is not uniform, and the foaming degree is low compared to the amount of the fine particles added when the organic / inorganic fine particles are conventionally used as the foam nucleating agent. Without generation, it is possible to produce a foamed resin body (foamed insulator) having a small cell diameter, a uniform foaming degree, a high foaming degree, and a low dielectric constant.

  Next, a foam insulated wire using the foamed resin composition of the present invention will be described.

  FIG. 1 is a cross-sectional view of a foam insulated wire according to the present embodiment.

  As shown in FIG. 1, the foam insulated wire 1 includes a conductor 2 and a foam insulator 3 coated on the outer periphery of the conductor 2.

  The conductor 2 is made of a single wire or a stranded copper wire. As the conductor 2, besides a copper wire, an aluminum wire, a silver wire, various alloy wires, and a tube-like conductor can be used depending on the case. The surface may be plated with aluminum, silver, tin, or any other kind. It is also possible to use a copper-coated aluminum wire in which the surface of the aluminum wire is coated with copper.

  The foamed insulator 3 is supplied to a molding machine (for example, a foaming extruder) with the foamed resin composition of the present invention, and a foaming gas is press-fitted into the molding machine to perform foaming extrusion. Extruded and contains a large number of bubbles.

  The foamed insulator 3 may be a single layer or a combination of a plurality of foamed layers. Furthermore, you may form the coating layer which is not foamed or has a small foaming degree compared with a foamed layer in the inner peripheral part of the foamed insulator 3, and an outer peripheral part.

  The foaming degree of the foamed insulator 3 is preferably 50% or more and 90% or less. This is because if the foaming degree of the foamed insulator 3 is less than 50%, the dielectric constant of the foamed insulator 3 increases, and if it exceeds 90%, the mechanical strength often decreases. However, the present invention is not limited to this, and can be appropriately changed according to various characteristics required of the foamed insulator 3.

  In the foam insulated wire 1 according to the present embodiment, since the foam insulation 3 is made of the foamed resin composition of the present invention, the bubble diameter is small, the foaming degree is uniform, the foaming degree is high, and the dielectric constant is low. .

  That is, the foam insulated wire 1 according to the present embodiment has a low skew and is suitable as a high-speed transmission wire.

  Moreover, this invention is applicable not only to the foam insulated wire 1 but to a cable (for example, a coaxial cable).

  As shown in FIG. 2, the coaxial cable 21 according to the present embodiment has an inner skin that is not foamed or has a lower degree of foaming than the foamed insulator 3 at the inner and outer peripheral parts of the foamed insulator 3. A layer 22 and an outer skin layer 23 are formed, and an outer conductor 24 and a sheath 25 are sequentially formed on the outer periphery of the outer skin layer 23.

  The outer conductor 24 can be arbitrarily selected from horizontal winding, braiding, metal fine particle baking, metal foil / metal plate winding, etc. according to the application and required performance.

  Further, the inner skin layer 22 or the outer skin layer 23 can be omitted.

  The material of the sheath 25 can be any material such as polyolefin such as polyethylene or polypropylene, fluororesin, or polyvinyl chloride, and if necessary, a colorant, antioxidant, viscosity modifier, reinforcing material, filler, plastic (Softener), vulcanizing agent, vulcanization accelerator, crosslinking agent, crosslinking aid, foaming aid, processing aid, anti-aging agent, heat stabilizer, weathering stabilizer, antistatic agent, lubricant, UV absorption Agents, light stabilizers, flame retardants, surfactants, compatibilizers (compatibilizers), and other additives may be added as appropriate.

  Since the coaxial cable 21 according to the present embodiment uses the foamed resin composition of the present invention for the foamed insulator 3, the coaxial cable 21 has a low skew similarly to the foamed insulated wire 1 of FIG. 1.

  Here, although the coaxial cable 21 was demonstrated as an example, it is not limited to this, The structure is arbitrary.

  Examples of the present invention and comparative examples are shown below.

  Table 1 shows the manufacturing conditions and target values of the foam insulated wires experimentally produced in the examples and comparative examples.

The single-screw kneaders used in the examples and comparative examples are as follows.
Diameter: 40mm
L / D: 29

  Regarding the “bubble diameter”, first, five sample cross sections taken from a prototype foam insulated wire with a sufficient interval (1000 m or more) are taken with an SEM (manufactured by Hitachi High-Technologies Corporation: SN-3000).

  After that, let the image analysis software (Mitani Corporation: WinROOF) read the reference scale, calculate the length per pixel (pixel), and then read the SEM image that was taken, mainly manually to create the bubble outline The bubble area was calculated, and the diameter (equivalent circle diameter) when a circle with the same area was assumed was calculated.

  The average equivalent circle diameter of bubbles included in each of the five photographed SEM images and the average equivalent circle diameter of bubbles included in all five SEM images were calculated.

  The bubble diameter of 100 μm or less was accepted (◯), and the others were rejected (×).

  About "foaming degree fluctuation | variation", the fluctuation value of the foaming degree of the part (10000m) of the same length was compared from the foaming degree data at the time of electric wire trial manufacture.

  Specifically, at the time of trial production of a foam insulated wire, the capacitance and outer diameter are measured at intervals of 1 s, and the foaming degree at each moment is determined from the conductor diameter, outer diameter, capacitance, and relative dielectric constant of the base resin. Is calculated.

  To what extent the calculated maximum value and minimum value of the foaming degree fluctuated with respect to the average value was determined and used as the fluctuation value of the foaming degree.

  In the example and the comparative example, since the average foaming degree is 60%, only the variation value is displayed.

  The foaming degree of 59.0 to 61.0% was determined to be acceptable (◯), and the others were regarded as unacceptable (x).

  Tables 2 and 3 show configurations and evaluation results of Examples and Comparative Examples.

  Comparing Example 1 in which the melting point of the base resin is lower than the melting point of the different polymer material and Comparative Example 1 in which the melting point of the base resin is higher than the melting point of the different polymer material, the example in all the bubble diameter and foaming degree fluctuations 1 is excellent.

  In Example 1, during the resin extrusion, the crystallization of the different polymer material occurs earlier than the crystallization of the base resin, and the foaming gas is expelled from the different polymer material. While the foaming gas concentration of the base resin in the vicinity of the interface with the molecular material increases and bubbles are generated, in Comparative Example 1, the order of crystallization of the different polymer material and the base resin is reversed, so the vicinity of the interface This is probably because no bubbles were generated.

  Example 2 and Comparative Example 2 with a resin nucleating agent concentration of 1 mass%, Example 3 and Comparative Example 3 with a resin nucleating agent concentration of 20 mass%, Example 4 and Comparative Example 4 with a resin nucleating agent concentration of 45 mass% The same can be said even if these are compared.

  Comparing Example 5 in which the processing temperature of the foamed resin composition exceeds the melting point of the different polymer material and Comparative Example 5 in which the processing temperature of the foamed resin composition is lower than the melting point of the different polymer material, the cell diameter and the degree of foaming Example 5 is superior in all variations.

  In Example 5, foaming gas dissolves in different polymer materials and bubbles are generated during resin extrusion, whereas in Comparative Example 5, foaming gas is generated in different polymer materials. It is thought that this is because no bubbles are generated without being dissolved.

  Example 6 and Comparative Example 6 with a resin nucleating agent concentration of 1 mass%, Example 7 and Comparative Example 7 with a resin nucleating agent concentration of 20 mass%, Example 8 and Comparative Example 8 with a resin nucleating agent concentration of 45 mass% The same can be said even if these are compared.

  From the above, according to the present invention, a simple method is used in which different types of polymer materials that are uniformly dispersed in the base resin by kneading are kneaded into the base resin, and bubbles are generated at the interface using the difference in physical properties between the two. Thus, it can be seen that a foamed resin composition capable of producing a foamed resin (foamed insulator) with a low cost, a high degree of foaming, and a small cell diameter can be obtained.

  Therefore, an electric wire for high-speed transmission can be produced by forming a foamed insulator using the foamed resin composition of the present invention.

1 Foam insulated wire 2 Conductor 3 Foam insulator

Claims (4)

A different polymer material is kneaded into the base resin with respect to the base resin, processed at a predetermined processing temperature and injected with a foaming gas, so that the different polymer material dispersed in the base resin A foamed resin composition for foaming and forming a foam by foaming from the surroundings is a method for producing a foam insulated wire in which a foam insulation is coated on the outer periphery of a conductor ,
The base resin is made of a polyolefin resin, and the dissimilar polymer material is one of polybutylene, cellulose, cellulose acetate, cellulose butylacetate, and polylactic acid, and the melting point of the dissimilar polymer material is the base. A method for producing a foam insulated wire, characterized by being within the range of the melting point of the resin and the processing temperature. A different polymer material is kneaded into the base resin with respect to the base resin, processed at a predetermined processing temperature and injected with a foaming gas, so that the different polymer material dispersed in the base resin A foamed resin composition for foaming and forming a foam by foaming from the surroundings is a method for producing a foam insulated wire in which a foam insulation is coated on the outer periphery of a conductor ,
The base resin is made of a polyolefin resin, and the dissimilar polymer material is any one of polybutylene, cellulose, cellulose acetate, cellulose butylacetate, and polylactic acid, and the glass transition point of the dissimilar polymer material is A method for producing a foam insulated wire, wherein the melting point of the base resin is within the range of the processing temperature. The method for producing a foam insulated wire according to claim 1 or 2, wherein the dissimilar polymer material is 0.1 mass% or more and 45 mass% or less with respect to 100 mass% of the base resin and the dissimilar polymer material as a whole. The method for producing a foam insulated wire according to claim 1 , wherein the foam insulation has a foaming degree of 50% or more and 90% or less.

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